Do you happen to have any in-game references of how the Mass Combat system plays out? I see the rules, but I'm attempting to get a feeling of their use.

What types of effect does it have on the players? How fast of a resolution are you looking for? How much influence do you want the PC's to wield, especially for those in the front lines, commanders, and generals.

I don't have DnD Insider, but I do subscribe to the RSS feed. There is a new article that sounds like it may be what is being looked for here. The intro touts it as filling in gaps on running large scale warfare via skill challenges.

Excerpt from the public intro

Almost all of these rule sets struggled with one, important question: How do you drag a PC into the battle? After all, D&D is a game about individual adventurers. What effect does a 15th-level wizard have on battle? A 6th-level warden can chop through 1st-level goblin minions all day, but what happens when she leads 50 members of the local militia against 300 goblins?

The skill challenge mechanic is a good match for running the clash of armies, but on its own, it leaves huge swaths of information for the DM to fill in. What does the challenge represent? What's the cost of failure and the reward for victory? What exactly does each skill check cover during a big battle? Answering those questions is key to creating a skill challenge, but those answers might vary based on the battle's role in your campaign and the characters' roles in the battle.